Air China said Monday it has ordered 12 Airbus A330-300 long-haul wide-bodied jets worth $2.9 billion.

Air China, which is China's third largest carier by passengers carried, did not say in its statement to the Shanghai exchange if the order for 2016 through 2018 delivery was part of a deal for 30 A330 announced last October.

The prices are based on open market 2013 list prices which would be nearer $3.1 billion today but Air China indicated it had been granted price concessions in the form of credit memoranda following negotiations.

The carrier, which said it will pay for the new jets in instalments, also indicated the purchases from the European planemaker would "optimize its fleet structure" and strengthen capacity, boosting the latter by 5.6 percent.

Last October, China confirmed during a visit by German Chancellor Angela Merkel an order for 30 A330 jets confirming an outline agreement from June in Paris.

The initial outline agreement was for the sale of 75 A330 to public holding company China Aviation Supplies (CAS) for a catalogue value of $18 billion.